Nonaqueous electrolytic liquid and nonaqueous electrolyte secondary battery

Abstract

A nonaqueous electrolytic liquid according to the present disclosure includes a nonaqueous solvent, an electrolyte that is dissolved in the nonaqueous solvent, and particles of an oxide that is insoluble in the nonaqueous solvent. This nonaqueous electrolytic liquid is fluid at 25° C. The molar mass of the oxide is 50 g / mol or greater. The average particle diameter of the particles of the oxide is 1 nm to 500 nm. A secondary battery 100 according to the present disclosure comprises a positive electrode 5, a negative electrode 6, and the nonaqueous electrolytic liquid according to the present disclosure.

Description

Nonaqueous electrolyte and nonaqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte solution and a non-aqueous electrolyte secondary battery.

[0002] Batteries using non-aqueous electrolytes have high voltage and high energy density, and research and development into these batteries is being actively conducted. For example, efforts are being made to improve the battery characteristics of lithium secondary batteries by improving the electrolyte.

[0003] Patent Document 1 discloses a nonaqueous electrolyte secondary battery having a negative electrode and a positive electrode made of either metallic lithium or a non-graphitizable carbon material, and a nonaqueous electrolyte. Patent Document 1 discloses that a nonaqueous electrolyte secondary battery containing vinylene carbonate as a nonaqueous solvent has good cycle characteristics. Patent Document 2 discloses an ion secondary battery comprising a positive electrode made of a composite lithium oxide or composite sodium oxide, a negative electrode made of a material capable of retaining lithium or sodium, a separator, and an electrolyte made of a nonaqueous solvent, the electrolyte containing fluoroethylene carbonate and phosphorus compound particles. Patent Document 3 discloses a lithium secondary battery with an organic electrolyte containing alumina-based fine particles. Patent Document 4 discloses a nonaqueous electrolyte secondary battery using an electrolyte containing one or more oxides selected from Al2O3, BaO, and MgO. Patent Document 5 discloses a nonaqueous electrolyte secondary battery using a nonaqueous electrolyte composition containing an electrolyte salt, a nonaqueous solvent, a matrix polymer, and a ceramic powder. Patent Document 6 discloses a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte composition containing a non-aqueous solvent, an electrolyte salt, a matrix resin, a surfactant, and ceramic powder as a filler.

[0004] Japanese Patent Laid-Open No. 2005-268230 Japanese Patent Laid-Open No. 2012-018801 Japanese Patent Laid-Open No. 10-334730 Japanese Patent Laid-Open No. 04-284372 Japanese Patent Laid-Open No. 2010-198757 Japanese Patent Laid-Open No. 2010-257838

[0005] The present disclosure provides a nonaqueous electrolyte suitable for improving the charge / discharge efficiency of a battery.

[0006] The nonaqueous electrolyte solution of the present disclosure includes a nonaqueous solvent, an electrolyte dissolved in the nonaqueous solvent, and oxide particles insoluble in the nonaqueous solvent, and has fluidity at 25°C, wherein the oxide has a molar mass of 50 g / mol or more, and the particles have an average particle size of 1 nm or more and 500 nm or less.

[0007] According to the technology of the present disclosure, the charge and discharge efficiency of a battery can be improved.

[0008] Fig. 1 is a schematic cross-sectional view showing an example of a nonaqueous electrolyte secondary battery according to Embodiment 2. Fig. 2 is a graph showing the results of cycle tests of Example 1 and Comparative Example 1.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0010] (Embodiment 1) The nonaqueous electrolyte solution of Embodiment 1 contains a nonaqueous solvent, an electrolyte dissolved in the nonaqueous solvent, and oxide particles insoluble in the nonaqueous solvent. The molar mass of the oxide is 50 g / mol or more. The average particle diameter of the oxide particles is 1 nm or more and 500 nm or less. The nonaqueous electrolyte solution of Embodiment 1 has fluidity at 25°C. Use of the nonaqueous electrolyte solution of Embodiment 1 in a battery can improve charge / discharge efficiency and, in turn, cycle characteristics. Furthermore, the nonaqueous electrolyte solution of Embodiment 1 has improved dispersibility of the oxide particles, which can also increase the industrial productivity of the nonaqueous electrolyte solution.

[0011] In the present disclosure, "having fluidity at 25°C" means having a viscosity of 20,000 mPa·s or less at 25°C.

[0012] The viscosity of the nonaqueous electrolyte in embodiment 1 at 25°C may be, for example, 5000 mPa·s or less, 3000 mPa·s or less, or 1000 mPa·s or less. The nonaqueous electrolyte in embodiment 1 is, for example, a liquid. Liquids also include sols. That is, the nonaqueous electrolyte in embodiment 1 is a nonaqueous colloidal solution in which oxide particles are dispersed.

[0013] In the present disclosure, "oxide particles insoluble in a non-aqueous solvent" refers to oxide particles that require 100 mL or more of non-aqueous solvent to dissolve 1 g of the oxide particles at 25°C. That is, the solubility of the oxide particles in 100 mL of non-aqueous solvent is 1 g or less. Here, "dissolution" means that the permeability of the solution obtained when the oxide particles are dissolved in the non-aqueous solvent in a container does not change from the permeability of the solvent, that is, the solution is not cloudy, and no precipitate is observed on the bottom of the container after standing for 24 hours.

[0014] The oxide particles may be oxide particles having a solubility of 0.1 g or less in 100 mL.

[0015] The oxide may contain a metal element or a metalloid element. In the present disclosure, "metalloid elements" are B, Si, Ge, As, Sb, and Te. "Metal elements" are all elements in Groups 1 to 12 of the periodic table excluding hydrogen, and all elements in Groups 13 to 16 of the periodic table excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. The oxide may include an oxide of an element selected from the group of elements in Periods 3 to 6 of the periodic table.

[0016] The oxide may include at least one oxide selected from the group consisting of Zr, Al, Si, Ca, Ti, Zn, Y, Nb, Fe, Hf, Mg, Mn, Na, B, and W. The oxide may include at least one oxide selected from the group consisting of Zr and Al.

[0017] The oxide may include at least one selected from the group consisting of ZrO2 and Al2O3. That is, the nonaqueous electrolyte in embodiment 1 may include particles of at least one selected from the group consisting of ZrO2 and Al2O3. According to the above configuration, the charge / discharge efficiency of the battery can be improved. The oxide may be ZrO2.

[0018] An oxide with a molar mass of less than 50 g / mol may dissolve in trace amounts of moisture if detected inside the battery. In the nonaqueous electrolyte of embodiment 1, the oxide has a molar mass of 50 g / mol or more, so even if a trace amount of moisture is present inside the battery, the oxide particles do not dissolve in the moisture. This allows the oxide particles to affect the coordination environment between Li ions and the solvent, thereby improving the charge / discharge efficiency of the battery. An example of an oxide with a molar mass of less than 50 g / mol is LiO.

[0019] In the non-aqueous electrolyte solution of embodiment 1, the oxide particle content may be 0.1 vol% or more and 10 vol% or less. The oxide particle content may be 0.1 vol% or more and 8 vol% or less, 0.5 vol% or more and 6 vol% or less, 1 vol% or more and 5 vol% or less, or 1 vol% or more and 4 vol% or less. The above configuration can improve the dispersibility of the oxide particles and the fluidity of the non-aqueous electrolyte solution.

[0020] The content of oxide particles in the non-aqueous electrolyte in embodiment 1 can be determined, for example, by the following method: The non-aqueous electrolyte is filtered to separate the particles. The separated particles are washed with a solvent such as dimethyl carbonate, and the washing solvent is evaporated and dried, after which the mass of the particles is measured. The volume of the particles is calculated from the specific gravity determined from the mass of the particles and the particle components. The particle components can be determined by various analytical methods such as inductively coupled plasma analysis (ICP), X-ray diffraction (XRD), infrared absorption spectroscopy (IR), and nuclear magnetic resonance analysis (NMR). In this way, the content of oxide particles in the non-aqueous electrolyte can be calculated. The volume of the non-aqueous electrolyte can also be calculated from the composition and mass. The composition of the non-aqueous electrolyte can be measured using a liquid chromatograph, gas chromatograph, or the like.

[0021] When the average particle size of the oxide particles is 500 nm or less, the oxide particles can penetrate into the electrode group when the nonaqueous electrolyte penetrates into the electrode group in a battery using the nonaqueous electrolyte of the present disclosure. Therefore, the oxide particles can affect the coordination environment between Li ions and the solvent even around the positive electrode active material and the negative electrode active material arranged inside the electrode group. The average particle size of the oxide particles may be 5 nm or more and 400 nm or less, or may be 10 nm or more and 300 nm or less.

[0022] The average particle size of the oxide particles may be smaller than the average particle size of the cathode active material of the battery described below in which the nonaqueous electrolyte of embodiment 1 is used. The average particle size of the oxide particles may be 25% or less, 10% or less, 5% or less, or 1% or less of the average particle size of the cathode active material. Here, the cathode active material is a secondary particle formed by aggregation of primary particles, and the "average particle size of the cathode active material" refers to the average particle size of the secondary particles. Oxide particles are typically insulators. Therefore, by making the average particle size of the oxide particles smaller than the average particle size of the cathode active material, an increase in the resistance of the cathode surface can be suppressed, and charge / discharge efficiency can be further improved.

[0023] The average particle size of the oxide particles may be equal to or smaller than the pore size of the separator of a battery using a nonaqueous electrolyte. With this configuration, the oxide particles do not clog the pores of the separator, and therefore circulation of the electrolyte inside the electrode group during charge and discharge is not hindered.

[0024] In the present disclosure, the average particle size refers to the median diameter (d50). The median diameter is the particle diameter at which the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution can be determined by a laser diffraction scattering method using a commercially available laser diffraction measuring device.

[0025] The electrolyte may include, for example, a lithium salt. Examples of lithium salts include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisperfluoroethylsulfonylimide (LiN(SO2C2F5)2), LiAsF6, LiCF3SO3, and lithium difluoro(oxalato)borate. The electrolyte may include at least one selected from the substances listed above as lithium salts. The lithium salt may include fluorine (F). The lithium salt may be LiPF6.

[0026] The concentration of the lithium salt in the nonaqueous electrolyte may be, for example, 0.5 mol / L or more and 2 mol / L or less. By controlling the lithium salt concentration within the above range, an electrolyte having excellent ionic conductivity and appropriate viscosity can be obtained. However, the lithium salt concentration is not limited to the above.

[0027] The non-aqueous solvent is not particularly limited, and for example, a cyclic carbonate, a chain carbonate, a cyclic carboxylic acid ester, or the like may be used.

[0028] Examples of the cyclic carbonate include propylene carbonate (PC) and ethylene carbonate (EC).

[0029] Examples of the chain carbonate ester include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC).

[0030] Examples of the cyclic carboxylic acid ester include γ-butyrolactone (GBL) and γ-valerolactone (GVL).

[0031] The non-aqueous solvent may be used alone or in combination of two or more. The non-aqueous solvent may contain ethylene carbonate. This can increase the solubility of the electrolyte in the non-aqueous solvent.

[0032] The nonaqueous electrolyte solution in embodiment 1 may further contain other substances in addition to those described above. For example, the nonaqueous electrolyte solution in embodiment 1 may further contain an additive to improve the dispersibility of oxide particles. The additive is, for example, a fluorine-containing solvent. That is, the nonaqueous electrolyte solution in embodiment 1 may further contain a fluorine-containing solvent. With the above configuration, it is possible to reduce aggregation of oxide particles and the resulting sedimentation of the particles over time.

[0033] Examples of fluorine-containing solvents include fluorinated ethers, which may include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether.

[0034] The nonaqueous electrolyte solution in the first embodiment can be produced, for example, by the following method.

[0035] A lithium salt is dissolved in a non-aqueous solvent. The resulting solution is mixed with oxide particles, such as ZrO particles, and ZrO balls as a mixing medium in a ball mill. The mixing medium is removed from the resulting mixture to obtain the non-aqueous electrolyte solution of embodiment 1.

[0036] The method for producing the non-aqueous electrolyte is not limited to the above, and may be, for example, by dispersing oxide particles in a non-aqueous solvent in which a lithium salt has been dissolved, using an ultrasonic homogenizer.

[0037] (Embodiment 2) A nonaqueous electrolyte secondary battery according to Embodiment 2 includes a positive electrode, a negative electrode, and the nonaqueous electrolyte solution according to Embodiment 1. By using the nonaqueous electrolyte solution according to Embodiment 1, the charge / discharge efficiency of the secondary battery can be improved.

[0038] FIG. 1 is a schematic cross-sectional view showing an example of a nonaqueous electrolyte secondary battery according to Embodiment 2. The secondary battery 100 includes a container 1, an electrode group 4, and an electrolyte solution (not shown). The electrolyte solution is the nonaqueous electrolyte solution of Embodiment 1. The electrode group 4 has a wound structure. The electrode group 4 is housed in the container 1. The electrode group 4 includes a positive electrode 5, a negative electrode 6, and a pair of separators 7. The electrode group 4 is impregnated with the electrolyte solution. The opening of the container 1 is closed with a sealing plate 2. The positive electrode 5 includes a positive electrode current collector 5a and a positive electrode active material layer 5b. One end of a positive electrode lead 5c is connected to the positive electrode 5. The other end of the positive electrode lead 5c is connected to the back surface of the sealing plate 2. An insulating packing 3 is disposed around the sealing plate 2. The negative electrode 6 includes a negative electrode current collector 6a and a negative electrode active material layer 6b. One end of the negative electrode lead 6c is connected to the negative electrode 6. The other end of the negative electrode lead 6c is connected to the bottom surface of the container 1. An insulating ring 8 is disposed on each of the upper and lower surfaces of the electrode group 4.

[0039] Each component of the secondary battery 100 will be specifically described below.

[0040] The positive electrode current collector 5a can be a sheet or film made of a metal material such as aluminum, stainless steel, titanium, or an alloy thereof. Aluminum and its alloys are suitable materials for the positive electrode current collector 5a because they are inexpensive and easy to form into thin films. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material such as carbon may be applied to the surface of the positive electrode current collector 5a as a conductive auxiliary material.

[0041] The positive electrode active material layer 5b includes a positive electrode active material. The positive electrode active material may be a material capable of absorbing and releasing lithium ions. Examples of the positive electrode active material include lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. In particular, using a lithium-containing transition metal oxide or a lithium-containing transition metal phosphate as the positive electrode active material can reduce the manufacturing cost of the battery and increase the average discharge voltage. Examples of lithium-containing transition metal oxides include lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium nickel manganese oxide. Examples of lithium-containing transition metal phosphates include lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate.

[0042] The positive electrode active material may contain lithium nickel oxide having a layered rock salt crystal structure. The proportion of Ni among metal elements other than Li contained in the lithium nickel oxide may be 50 atomic % or more. The lithium nickel oxide may also contain other transition metals. The lithium nickel oxide is useful for achieving a high operating voltage.

[0043] The lithium nickel oxide may be represented by the following composition formula (I): Element M1 is at least one selected from the group consisting of V, Co, and Mn. Element M2 is at least one selected from the group consisting of Mg, Al, Ca, Ti, Cu, Zn, and Nb. Composition formula (I) satisfies 0.9≦α≦1.10, −0.05≦β≦0.05, 0.5≦x1<1, 0≦x2≦0.5, and 0<1−x1−x2≦0.5.

[0044] Li α Ni x1 M1 x2 M2 (1-x1-x2) O 2+β ...(I)

[0045] The positive electrode active material may be secondary particles formed by aggregation of primary particles. The particle size of the primary particles constituting the secondary particles is, for example, 0.02 μm or more and 2 μm or less. The particle size of the primary particles is measured as the diameter of a circumscribed circle in a particle image observed with a scanning electron microscope (SEM). The average particle size of the secondary particles of the positive electrode active material may be, for example, 2 μm or more and 30 μm or less, more than 2 μm and 20 μm or less, or 3 μm or more and 10 μm or less.

[0046] The positive electrode active material layer 5b may contain other materials such as a conductive additive and a binder.

[0047] The conductive additive is used to reduce the resistance of the positive electrode 5. Examples of the conductive additive include a carbon material and a conductive polymer compound. Examples of the carbon material include carbon black, graphite, acetylene black, carbon nanotubes, carbon nanofibers, graphene, fullerene, and graphite oxide. Examples of the conductive polymer compound include polyaniline, polypyrrole, and polythiophene.

[0048] The binder is used to improve the binding property of the material constituting the positive electrode 5. As the binder, polymer materials such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, styrene-butadiene copolymer rubber, polypropylene, polyethylene, and polyimide can be used.

[0049] The negative electrode current collector 6a may be a sheet or film made of a metal material such as stainless steel, nickel, copper, or an alloy thereof. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material such as carbon may be applied to the surface of the negative electrode current collector 6a as a conductive auxiliary material.

[0050] The negative electrode active material layer 6b includes a negative electrode active material. The negative electrode active material can be a material capable of absorbing and releasing lithium ions. The negative electrode active material includes, for example, at least one selected from the group consisting of carbon materials and materials capable of forming an alloy with lithium. Examples of carbon materials include graphite. Examples of materials capable of forming an alloy with lithium include silicon, silicon-containing oxides, tin, zinc alloys, bismuth, and germanium. One type selected from these negative electrode active materials may be used, or two or more types may be used in combination.

[0051] The negative electrode active material layer 6b may contain at least one selected from the group consisting of graphite and silicon as the negative electrode active material. The negative electrode active material layer 6b may contain only graphite as the negative electrode active material. Graphite is recommended because it is resistant to deterioration even when repeatedly charged and discharged at a deep depth. Carbon materials other than graphite may also be used as the negative electrode active material. Silicon has a larger capacity than graphite and is therefore advantageous for increasing the capacity of the secondary battery 100.

[0052] The negative electrode active material layer 6b may contain other materials such as a conductive additive, a binder, etc. Materials that can be used as the conductive additive and binder for the positive electrode active material layer 5b can also be used for the negative electrode active material layer 6b.

[0053] The electrolyte is the nonaqueous electrolyte in embodiment 1. The electrolyte is impregnated into the positive electrode 5, the negative electrode 6, and the separator 7. The electrolyte may fill the internal space of the container 1. The electrolyte allows lithium ions to move between the positive electrode 5 and the negative electrode 6.

[0054] The average particle size of the oxide particles contained in the electrolyte may be equal to or smaller than the pore size of the separator 7 .

[0055] The separator 7 has lithium ion conductivity. The material of the separator 7 is not particularly limited as long as it allows the passage of lithium ions. The material of the separator 7 can be at least one selected from the group consisting of a gel electrolyte, an ion exchange resin membrane, a semipermeable membrane, and a porous membrane. Making the separator 7 from these materials can sufficiently ensure the safety of the secondary battery 100. Examples of gel electrolytes include gel electrolytes containing fluororesins such as PVdF. Examples of ion exchange resin membranes include cation exchange membranes and anion exchange membranes. Examples of porous membranes include porous membranes made of polyolefin resins and porous membranes containing glass paper obtained by weaving glass fibers into nonwoven fabric.

[0056] The container 1 is made of a metal such as aluminum or stainless steel, and may have a cylindrical shape or a rectangular tube shape.

[0057] The electrode group 4 may be wound into a cylindrical shape or an oval shape.

[0058] The shape of the secondary battery 100 is not particularly limited. In the present disclosure, as an example of the structure of the nonaqueous electrolyte secondary battery according to embodiment 2, the configuration example shown in FIG. 1 is described, i.e., a secondary battery in which an electrode group formed by winding a positive electrode and a negative electrode with a separator interposed therebetween and an electrolyte solution are housed in an exterior body. However, the secondary battery according to the present disclosure is not limited to this configuration example. The secondary battery according to the present disclosure may have any shape, such as a cylindrical shape, a prismatic shape, a coin shape, a button shape, a laminate shape, or the like. Furthermore, as the electrode group in the secondary battery according to the present disclosure, instead of a wound-type electrode group, an electrode group of another shape, such as a stacked-type electrode group formed by stacking a positive electrode and a negative electrode with a separator interposed therebetween, may be used.

[0059] (Embodiment 3) A nonaqueous electrolyte secondary battery according to Embodiment 3 includes a positive electrode including a positive electrode current collector and a positive electrode active material layer, a negative electrode, and a nonaqueous electrolyte. The positive electrode active material layer is provided on the positive electrode current collector and includes a positive electrode active material. The positive electrode active material includes secondary particles formed by aggregation of primary particles. The nonaqueous electrolyte includes a nonaqueous solvent, an electrolyte dissolved in the nonaqueous solvent, and oxide particles insoluble in the nonaqueous solvent, and has fluidity at 25°C. The molar mass of the oxide is 50 g / mol or more, and the average particle size of the oxide particles is 25% or less of the average particle size of the secondary particles. The nonaqueous electrolyte secondary battery according to Embodiment 3 includes an electrolyte including the oxide particles, thereby achieving improved charge / discharge efficiency. It also improves cycle characteristics. Furthermore, it may improve charge / discharge efficiency without increasing the possibility of short-circuiting the battery.

[0060] The average particle size of the oxide particles contained in the nonaqueous electrolyte may be 1 nm or more and 500 nm or less, and may be 10% or less, 5% or less, or 1% or less of the average particle size of the secondary particles.

[0061] 1 is used as an example of the nonaqueous electrolyte secondary battery according to Embodiment 3. The descriptions of the positive electrode 5, positive electrode current collector 5a, positive electrode active material layer 5b, negative electrode 6, and electrolyte of the secondary battery 100 in Embodiment 2 can be applied to the descriptions of the positive electrode, positive electrode current collector, positive electrode active material layer, negative electrode, and nonaqueous electrolyte of the nonaqueous electrolyte secondary battery according to Embodiment 3. That is, the descriptions of Embodiment 1 can be applied to the same components of the nonaqueous electrolyte included in the nonaqueous electrolyte secondary battery according to Embodiment 3.

[0062] The application of the nonaqueous electrolyte solution of the present disclosure is not limited to the secondary battery 100. In addition to lithium secondary batteries, the nonaqueous electrolyte solution of the present disclosure can be applied to various secondary batteries such as sodium secondary batteries and magnesium secondary batteries. Therefore, the nonaqueous electrolyte secondary battery of the present disclosure can be various secondary batteries such as sodium secondary batteries and magnesium secondary batteries in addition to lithium secondary batteries.

[0063] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0064] (Technology 1) A non-aqueous electrolyte solution comprising: a non-aqueous solvent; an electrolyte dissolved in the non-aqueous solvent; and oxide particles insoluble in the non-aqueous solvent; the non-aqueous electrolyte solution has fluidity at 25°C; the oxide has a molar mass of 50 g / mol or more; and the particles have an average particle size of 1 nm or more and 500 nm or less.

[0065] This configuration improves the charge / discharge efficiency of the battery, and also improves the dispersibility of oxide particles in the non-aqueous electrolyte, making it possible to increase industrial productivity.

[0066] (Technology 2) The nonaqueous electrolyte according to Technology 1, wherein the oxide contains at least one element selected from the group consisting of metal elements and semi-metal elements. With this configuration, the charge / discharge efficiency of the battery can be improved.

[0067] (Technology 3) The nonaqueous electrolyte according to Technology 1 or 2, wherein the oxide is at least one selected from the group consisting of ZrO2 and Al2O3. With this configuration, the charge / discharge efficiency of the battery can be improved.

[0068] (Technology 4) The nonaqueous electrolyte according to any one of Technologies 1 to 3, wherein the oxide is ZrO2. With this configuration, the charge / discharge efficiency of the battery can be improved.

[0069] (Technology 5) The nonaqueous electrolyte according to any one of Technologies 1 to 4, wherein the content of the particles in the nonaqueous electrolyte is 0.1% by volume or more and 10% by volume or less. With this configuration, the dispersibility of the oxide particles and the fluidity of the nonaqueous electrolyte can be improved.

[0070] (Technology 6) A non-aqueous electrolyte secondary battery comprising: a positive electrode; a negative electrode; and the non-aqueous electrolyte solution according to any one of Technologies 1 to 5.

[0071] This configuration can improve charge / discharge efficiency.

[0072] (Technology 7) A non-aqueous electrolyte secondary battery comprising: a positive electrode current collector; a positive electrode provided on the positive electrode current collector and including a positive electrode active material layer containing a positive electrode active material; a negative electrode; and a non-aqueous electrolyte solution, wherein the positive electrode active material includes secondary particles formed by aggregation of primary particles; the non-aqueous electrolyte solution includes: a non-aqueous solvent; an electrolyte dissolved in the non-aqueous solvent; and oxide particles insoluble in the non-aqueous solvent; the non-aqueous electrolyte solution has fluidity at 25°C; the molar mass of the oxide is 50 g / mol or more; and the average particle size of the oxide particles is 25% or less of the average particle size of the secondary particles.

[0073] This configuration can improve charge / discharge efficiency, improve cycle characteristics, and further improve charge / discharge efficiency without increasing the possibility of short-circuiting the battery.

[0074] (Technology 8) The nonaqueous electrolyte secondary battery according to Technology 7, wherein the oxide contains at least one element selected from the group consisting of metal elements and semi-metal elements. With this configuration, charge / discharge efficiency can be improved.

[0075] (Technology 9) The nonaqueous electrolyte secondary battery according to Technology 7 or 8, wherein the oxide is at least one selected from the group consisting of ZrO2 and Al2O3. With this configuration, charge / discharge efficiency can be improved.

[0076] (Technology 10) The nonaqueous electrolyte secondary battery according to any one of Technologies 7 to 9, wherein the oxide is ZrO2. With this configuration, charge / discharge efficiency can be improved.

[0077] (Technology 11) The nonaqueous electrolyte secondary battery according to any one of Techniques 7 to 10, wherein the content of the particles in the nonaqueous electrolyte is 0.1% by volume or more and 10% by volume or less. With this configuration, the dispersibility of the oxide particles in the nonaqueous electrolyte and the fluidity of the nonaqueous electrolyte can be improved.

[0078] (Technology 12) The nonaqueous electrolyte secondary battery according to any one of Techniques 7 to 11, wherein the particles have an average particle size of 1 nm or more and 500 nm or less. This improves the dispersibility of oxide particles in the nonaqueous electrolyte, thereby enabling increased industrial productivity of the nonaqueous electrolyte and batteries using the same.

[0079] The present disclosure will be described in more detail below using examples. The following examples are merely examples of embodiments, and are not intended to limit the scope of the present disclosure.

[0080] Example 1 (Preparation of Nonaqueous Electrolyte) Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of EC:EMC:DMC = 20:5:75 to prepare a nonaqueous solvent. LiPF was dissolved in the resulting nonaqueous solvent to a concentration of 1 mol / L to obtain a solution. 10 g of the resulting solution, 2.37 g of ZrO2 particles (average particle diameter 15 nm) as oxide particles, and 70 g of ZrO2 balls (average particle diameter 0.5 mm) as mixing media were placed in a ball mill and mixed at 300 rpm for 2 hours. The ZrO2 balls were removed from the resulting mixture to obtain the nonaqueous electrolyte of Example 1. The nonaqueous electrolyte of Example 1 contained 4 vol% dispersed ZrO2 particles. The nonaqueous electrolyte of Example 1 had fluidity at 25°C.

[0081] (Preparation of test cell) LiNi 0.8 Mn 0.2 A cathode active material having a composition of O2, acetylene black (AB), and polyvinylidene fluoride (PVDF) were mixed with N-methyl-2-pyrrolidone (NMP) and stirred to prepare a cathode slurry. The cathode active material was secondary particles formed by aggregation of primary particles, and the average particle size of the secondary particles was 5 μm. The mass ratio of these materials in the cathode active material layer was cathode active material:AB:PVDF=96:2:2.

[0082] The positive electrode slurry was applied to the surface of an aluminum foil (1.45 cm x 1.45 cm), the coating was dried, and then rolled to form a positive electrode active material layer. In this way, a positive electrode was obtained.

[0083] A laminate half cell was fabricated using a positive electrode, a Li metal foil (2 cm × 2 cm, 200 μm thick) as a counter electrode, a separator, and the nonaqueous electrolyte solution of Example 1. A PP / PE / PP three-layer separator was used as the separator.

[0084] In this manner, the evaluation cell of Example 1 was obtained.

[0085] Example 2 A nonaqueous electrolyte solution of Example 2 was obtained in the same manner as in Example 1, except that the oxide particles were changed to 1.65 g of Al2O3 particles (average particle diameter 50 nm). 4 volume % of Al2O3 particles were dispersed in the nonaqueous electrolyte solution of Example 2. A test cell of Example 2 was obtained in the same manner as in Example 1 using the nonaqueous electrolyte solution of Example 2.

[0086] Comparative Example 1: EC, EMC, and DMC were mixed in a volume ratio of EC:EMC:DMC = 20:5:75 to prepare a nonaqueous solvent. LiPF was dissolved in the obtained nonaqueous solvent to a concentration of 1 mol / L to obtain a nonaqueous electrolyte solution of Comparative Example 1. That is, the nonaqueous electrolyte solution of Comparative Example 1 was prepared in the same manner as in Example 1, except that it did not contain oxide particles. A test cell of Comparative Example 1 was obtained using the nonaqueous electrolyte solution of Comparative Example 1 in the same manner as in Example 1.

[0087] [Evaluation of Charge / Discharge Characteristics] The evaluation cells of Examples 1 and 2 and Comparative Example 1 were charged at a constant current of 0.1 C at an ambient temperature of 25° C. until the voltage reached 4.5 V, and then discharged at a constant current of 0.1 C until the voltage reached 2.5 V. In this manner, the initial charge / discharge efficiency of the evaluation cells of Examples 1 and 2 and Comparative Example 1 was evaluated.

[0088] [Cycle Test] The evaluation cells of Example 1 and Comparative Example 1, which had been charged and discharged as described above, were changed to an ambient temperature of 55°C. These cells were charged at a constant current of 0.3 C until the voltage reached 4.5 V. Thereafter, they were discharged at a constant current of 0.3 C until the voltage reached 2.5 V. The above-described charge and discharge constituted one cycle, and this cycle was repeated 40 times to evaluate the discharge capacity, charge and discharge efficiency, and capacity retention rate.

[0089] Table 1 shows the evaluation results of the initial charge-discharge efficiency of the evaluation cells of Examples 1 and 2 and Comparative Example 1. The initial charge-discharge efficiency shown in Table 1 is a relative value when the initial charge-discharge efficiency of Comparative Example 1 is set to 100%. Table 2 shows the results of the cycle test of the evaluation cells of Example 1 and Comparative Example 1. FIG. 2 is a graph showing the results of the cycle test of Example 1 and Comparative Example 1. The capacity retention is a relative value when the discharge capacity at the second cycle of each test cell is set to 100%.

[0090]

[0091]

[0092] (Discussion) In the evaluation of charge / discharge characteristics, the secondary batteries of Example 1 and Example 2 had improved initial charge / discharge efficiency compared to the secondary battery of Comparative Example 1. Furthermore, in the cycle test, the secondary battery of Example 1 exhibited a larger discharge capacity than the secondary battery of Comparative Example 1, and had improved charge / discharge efficiency and capacity retention. It is believed that the battery characteristics were improved because the coordination environment between Li ions and the solvent was changed by the inclusion of oxide particles in the nonaqueous electrolyte. Based on the results of the initial charge / discharge efficiency, it is more preferable to use ZrO2 as the oxide.

[0093] The technology of the present disclosure is useful for, for example, lithium ion secondary batteries.

Claims

1. a non-aqueous solvent, an electrolyte dissolved in the non-aqueous solvent; and Particles of an oxide insoluble in the non-aqueous solvent; Including, It has fluidity at 25°C, The molar mass of the oxide is 50 g / mol or more, The average particle size of the particles is 1 nm or more and 500 nm or less, The content of the particles is 0.1% by volume or more and 10% by volume or less. Non-aqueous electrolyte.

2. The oxide contains at least one element selected from the group consisting of metal elements and metalloid elements. The nonaqueous electrolyte according to claim 1 .

3. The oxide is ZrO 2 and Al 2 O 3 At least one selected from the group consisting of: The nonaqueous electrolyte according to claim 1 .

4. The oxide is ZrO 2 That is, The nonaqueous electrolyte according to claim 1 .

5. positive electrode, a negative electrode, and The nonaqueous electrolyte solution according to any one of claims 1 to 4, Equipped with Nonaqueous electrolyte secondary battery.

6. a positive electrode including a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector and including a positive electrode active material; a negative electrode; a nonaqueous electrolyte; A non-aqueous electrolyte secondary battery comprising: the positive electrode active material includes secondary particles formed by aggregation of primary particles, The nonaqueous electrolyte solution is a non-aqueous solvent, an electrolyte dissolved in the non-aqueous solvent; and Particles of an oxide insoluble in the non-aqueous solvent; Including, The nonaqueous electrolyte has fluidity at 25°C, The molar mass of the oxide is 50 g / mol or more, the average particle size of the oxide particles is 25% or less of the average particle size of the secondary particles; Nonaqueous electrolyte secondary battery.

7. The oxide contains at least one element selected from the group consisting of metal elements and metalloid elements. The nonaqueous electrolyte secondary battery according to claim 6 .

8. The oxide is ZrO 2 and Al 2 O 3 At least one selected from the group consisting of: The nonaqueous electrolyte secondary battery according to claim 6 .

9. The oxide is ZrO 2 That is, The nonaqueous electrolyte secondary battery according to claim 6 .

10. The content of the particles in the nonaqueous electrolyte is 0.1% by volume or more and 10% by volume or less. The nonaqueous electrolyte secondary battery according to claim 6 .

11. The average particle size of the particles is 1 nm or more and 500 nm or less. The nonaqueous electrolyte secondary battery according to claim 6 .